I don't think Seth said sealed subs are bad. Just that you can get the same tight quick bass from a ported sub and generally save some money. There really is no such thing as tight quick sub. There is such a thing a as well designed sub, that is properly integrated into a system. This in turn gives the clean bass for music and movies.
What you should be looking at is a well designed sub for less than 500 and focus on positioning and getting a flat in room response. This will give you the clean tight sounding bass your looking for. You might also consider some sort of EQ for the sub to help with achieving a flat in room response.
Sealed subs can have large amounts of dynamic output they just need to be built in very robust fashion. This in turn causes the cost to go up. You can generally find a well designed ported sub for significantly cheaper.
I currently use a HSU STF-2 and it's very clean sounding sub for music and movies.
Here is good link discussing many of the myths about subwoofers.
http://www.audiopulse.com/know-how/subwoofer-driver-guide/myths-about-subwoofers/
